DE19957193A1 - Liquid crystal medium, useful for electro-optical applications comprises a mixture of compounds and contains at least one substituted 1,3-dioxane compound and one phenyl pyrimidine compound. - Google Patents

Abstract

A liquid crystal medium is based on a mixture of compounds having a positive dielectric anisotropy and contains at least one 1,3-dioxane compound substituted by cyclohexane and phenyl and one phenyl pyrimidine compound. A liquid crystal medium (I) is based on a mixture of polar compounds having a positive dielectric anisotropy, at least one of which is of formula (1) and at least one of which is of formula (2). An Independent claim is included for an electrotropic liquid crystal device that contains (I). R<1>,R<2> = 1-7C n-alkyl or n-alkoxy, 2-7C alkenyl, alkenyloxy or n-alkoxyalkyl. R<1> is preferably 2-5C n-alkyl and R<2> is 3-5C n-alkyl; X<1> = F, OCHF2 or OCF3, preferably F; Y<11>, Y<12> = H or F, preferably F; X<2> = 1-7C n-alkyl, 1-5C n-alkoxy, F or OCF3, preferably F

Description

The present invention relates to a liquid crystalline medium as well its use for electro-optical purposes and this medium containing advertisements.

Liquid crystals are mainly used as dielectrics in display devices used because the optical properties of such substances by a applied voltage can be influenced. Electro-optical device solutions based on liquid crystals are the best for those skilled in the art known and can be based on various effects. Such before directions are, for example, cells with dynamic scattering, DAP- Cells (deformation of erect phases), guest / host cells, TN cells with twisted nematic structure, STN cells ("super twisted nematic "), SBE cells (" superbirefringence effect ") and OMI cells ("optical mode interference"). The most common display devices are based on the Schadt-Helfrich effect and have a twisted nema table structure.

The liquid crystal materials must have good chemical and thermal properties Stability and good stability to electric fields and possess electromagnetic radiation. Furthermore, the liquid crystal materials have low viscosity and short duration in the cells talk times, low threshold voltages and high contrast give.

Furthermore, they should be used at normal operating temperatures, i. H. in one as wide a range below and above room temperature as possible have suitable mesophase, for example for those mentioned above Cells have a nematic or cholesteric mesophase. Because liquid Crystals are usually used as mixtures of several components It is important that the components work well with one another are miscible. Other properties, such as electrical conductivity, the dielectric anisotropy and optical anisotropy, depending on Cell type and area of application meet different requirements gen. For example, materials for cells with twisted nematic Structure has positive dielectric anisotropy and low elec have tric conductivity.

For example, for matrix liquid crystal displays with integrated are not linear elements for switching individual pixels (MLC displays) Media with large positive dielectric anisotropy, broad nematic Phases, relatively low birefringence, very high specific Resistance, good UV and temperature stability and low vapor pressure he wishes.

Such matrix liquid crystal displays are known. Active elements (ie transistors), for example, can be used as non-linear elements for the individual switching of the individual pixels. One then speaks of an "active matrix", whereby two types can be distinguished:

• 1.MOS (Metal Oxide Semiconductor) or other diodes on silicon Wafer as a substrate.
• 2. Thin film transistors (TFT) on a glass plate as a substrate.

The use of single crystal silicon as a substrate material be restricts the display size, as does the modular composition various partial displays on the joints leads to problems.

The more promising type 2, which is preferred, is called electro optical effect commonly used the TN effect. One distinguishes two technologies: TFTs made from compound semiconductors such as B. CdSe or TFTs based on polycrystalline or amorphous silicon. At the latter technology is being worked on with great intensity worldwide.

The TFT matrix is on the inside of one of the glass panels of the display applied, while the other glass plate on the inside is the trans Parent counter electrode carries. Compared to the size of the pixel Electrode, the TFT is very small and practically does not disturb the image. These Technology can also be expanded for fully color-capable images being a mosaic of red, green and blue filters like that is arranged that each filter element is a switchable picture element opposite is.

The TFT displays usually work as TN cells with crossed ones Polarizers in transmission and are backlit.

The term MLC displays here includes any matrix display with integrated non-linear elements, d. H. in addition to the active matrix, also displays with passive elements such as varistors or diodes (MIM = metal insulator Metal).

MLC displays of this type are particularly suitable for TV applications (e.g. pocket TV) or for high-information displays for computers applications (laptop) and in automobile or aircraft construction. Next to Problems with the angle dependence of the contrast and the Switching times result from difficulties with MFK displays insufficiently high specific resistance of the liquid crystal Mixtures [TOGASHI, S., SEKIGUCHI, K., TANABE, H., YAMAMOTO, E., SORIMACHI, K., TAJIMA, E., WATANABE, H., SHIMIZU, H., Proc. Eurodisplay 84, Sept. 1984: A 210-288 Matrix LCD Controlled by Double Stage Diode Rings, p. 141 ff, Paris; STROMER, M., Proc. Eurodisplay 84, Sept. 1984: Design of Thin Film Transistors for Matrix Addressing of Tele vision Liquid Crystal Displays, p. 145 ff, Paris]. With decreasing cons stand, the contrast of an MLC display deteriorates and it can the problem of "after image elimination" may occur. Since the specific Resistance of the liquid crystal mixture due to interaction with the inner surfaces of the display generally over the lifetime a MLC display decreases, a high (initial) resistance is very important important to obtain acceptable service life. Especially at low volt mixtures it was previously not possible to achieve very high specific Realizing resistances. It is also important that the specific Resistance as small an increase as possible with increasing temperature as well as after temperature and / or UV exposure. Especially after The low-temperature properties of the mixtures from the State of the art. It is required that even at low temperatures no crystallization and / or smectic phases occur and the Tem temperature dependence of the viscosity is as low as possible. The MFK displays state-of-the-art technology therefore does not meet today's requirements struggles.

There is therefore still a great need for MLC displays very high specific resistance with high work at the same time temperature range, short switching times even at low temperatures and lower threshold voltage, which does not have these disadvantages or only in show to a lesser extent.

In the case of TN (Schadt-Helfrich) cells, media are desired that allow the following advantages in the cells:

• - extended nematic phase range (especially too deep Temperatures)
• - Switchability at extremely low temperatures (out-door use, Automotive, avionics)
• - increased resistance to UV radiation (longer life duration).

With the media available from the prior art It is not possible to take advantage of these benefits while maintaining the rest Realize parameters.

In the case of more highly twisted cells (STN), media are desired that have a higher Multiplexability and / or lower threshold voltages and / or pulp tere nematic phase ranges (especially at low temperatures) enable. A further expansion of the is available for this standing parameter space (clearing point, transition smectic-nematic or melting point, viscosity, dielectric parameters, elastic parameters) urgently desired. In particular, mixtures that are large in size are desired Slopes of the electro-optical characteristic curve (characteristic curve slopes) and have low viscosities down to low temperatures.

The invention is based on the object, in particular for the media to provide like MFK, TN or STN displays that comply with the above given disadvantages or only to a lesser extent, and preferably at the same time very high specific resistances and low thresholds show tension.

It has now been found that this object can be achieved if media according to the invention are used in the advertisements as in claim 1 used as described.

The media according to the invention are distinguished in particular by the following properties

• - large nematic phase ranges,
• - low viscosities, which among other things lead to shorter switching times lead, and
• - good steepness of the characteristic curve.

The invention relates to a liquid-crystal medium based on a mixture of polar compounds with positive dielectric anisotropy, characterized in that it contains one or more, preferably two or more, compounds of the formula I

wherein
R ¹ n-alkyl or n-alkoxy with up to 7 carbon atoms, E-alkenyl, alkenyloxy or n-alkoxyalkyl with 2 to 7 carbon atoms, preferably n-alkyl with 2 to 5 carbon atoms,
X ¹ F, OCHF ₂ or OCF ₃ , preferably F and
Y ¹¹ and Y ¹² independently of one another are H or F, preferably at least one of the radicals Y ¹¹ and Y ¹² F, particularly preferably both F,
and one or more, preferably one, compounds of the formula II

wherein
R ^{2 has} the meaning given above for R ¹ in formula I and is preferably n-alkyl having 3 to 7, in particular 3 to 5, carbon atoms, and
X ² n-alkyl with 1 to 7 carbon atoms, n-alkoxy with 1 to 5 carbon atoms, F or OCF ₃ , preferably F,
means.

Another object of the invention is a liquid crystal display, in particular an MLC display containing one according to the invention Liquid crystal medium.

In addition to the compounds of the formulas I and II, the liquid-crystal media according to the invention preferably contain one or more compounds selected from the group of the compounds of the formulas III and IV, and particularly preferably also one or more compounds selected from the group of the compounds V and VI.

wherein
R ^{3 has} the meaning given above for R ¹ in formula I and preferably n-alkyl with 2 to 5 carbon atoms or 1 E-alkenyl with 2 to 5 carbon atoms,

X ³ OCHF ₂ or OCF ₃ , preferably OCF ₃ , and
Y ³¹ and Y ³² independently of one another are H or F
mean,

wherein
R ^{4 has} the meaning given above in formula III for R ³ and preferably the meaning preferred there,

and
Y ⁴ H or F, preferably H
mean,

wherein
R ⁵¹ and R ^52, independently of one another, have the meaning given ^{above for R 3 in formula III and R 51} preferably n-alkyl having 2 to 5 carbon atoms and R52 preferably 1 E alkenyl having 2 to 5, in particular 2 or 3 carbon atoms Atoms,

Z ⁵ -COO-, CH ₂ CH ₂ -, -CH = CH- or a single bond
mean.

wherein
R ⁶¹ and R ⁶² independently of one another have the ^{meaning given above in formula V for R 51} and R ⁵² and preferably n-alkyl having 2 to 5 carbon atoms,

Z ⁶ -COO- or a single bond, preferably -COO-,
mean.

Preferred liquid-crystal media according to the present application meet at least one of the following conditions, preferably two or three or more of these conditions:

The liquid crystal media contain

• a) one or more compounds selected from the group of formulas Ia to Ic
  where R1 has the meaning given above for formula 1,
  • - preferably one or more compounds of the formula Ib,
  • - particularly preferably three or more compounds of the formula Ib;
• b) one or more compounds of the formula IIa
  wherein alkyl is n-alkyl having 3 to 7 carbon atoms;
• c) one or more compounds selected from the group of formulas IIIa to IIIe
  wherein R ^{2 has} the meaning given above for formula III,
  • - preferably one or more compounds selected from the group of compounds IIIa to IIIc, preferably IIIa and IIIb, particularly preferably one or more compounds each of both the formula IIIa and the formula IIIb,
  • - very particularly preferably three or more compounds of both the formula IIIa and the formula IIIb;
• d) one or more compounds selected from the group of compounds of the formulas IVa to IVf
  wherein R ^{4 has} the meaning given above for formula IV,
  • - preferably one or more compounds selected from the group of compounds of the formulas IVa to IVc,
  • - particularly preferably in each case one or more compounds of the formulas IVa and IVc,
  • - very particularly preferably one or more compounds of the formula IVa in which R ^{4 is} alkenyl, and one or more compounds of the formula IVc;
• e) one or more compounds selected from the group of compounds IVg to IVj
  wherein R ^{4 has} the meaning given above for formula IV,
  • - preferably one or more compounds selected from the group of formulas IVg and IVh,
  • - particularly preferably one or more compounds of the formula IVg;
• f) one or more compounds selected from the group of compounds of the formulas Va to Vd
  wherein R ⁵¹ and R ^{52 have} the meaning given above for formula V,
  • - preferably one or more compounds selected from the group of compounds of the formulas Va and Vb,
  • - particularly preferably one or more compounds of the formula Va,
  • - very particularly preferably one or more compounds of the formula Va, where R ^{51 is} n-alkenyl and R ^{52 is} 1 E-alkenyl;
• g) one or more compounds selected from the group of compounds of the formulas VIa and VIb
  wherein R ⁶¹ and R ^{62 have} the meaning given above for formula VI,
  • - preferably one or more compounds of the formula VIa,
  • - particularly preferably two or more compounds of the formula VIa.

The liquid-crystal media can optionally contain one or more compounds of the formula VII

wherein
R ⁷¹ and R ^{72 have} the meaning given above in formula VI for R ⁶¹ and R ^{62 and}
LH or F means.

If one of the radicals R ¹ , R ² , R ³ , R ⁴ , R ⁵¹ , R ⁵² , R ⁶¹ , R ⁶² , R ⁷¹ and R ^{72 is} an alkyl radical and / or an alkoxy radical, this can be straight-chain or branched. It is preferably straight-chain, has 2, 3, 4, 5, 6 or 7 carbon atoms and is therefore preferably ethyl, propyl, butyl, pentyl, hexyl, heptyl, ethoxy, propoxy, butoxy, pentoxy, hexoxy or heptoxy, and also methyl , Octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, methoxy, octoxy, nonoxy, decoxy, undecoxy, dodecoxy, tridecoxy or tetradecoxy.

Oxaalkyl is preferably straight-chain 2-oxapropyl (= methoxy methyl), 2- (= ethoxymethyl) or 3-oxabutyl (= 2-methoxyethyl), 2-, 3- or 4-oxapentyl, 2-, 3-, 4- or 5-oxahexyl, 2-, 3-, 4-, 5- or 6-oxa heptyl, 2-, 3-, 4-, 5-, 6- or 7-oxaoctyl, 2-, 3-, 4-, 5-, 6-, 7- or 8-oxa nonyl, 2-, 3-, 4-, 5-, 6-, 7-, 8- or 9-oxadecyl.

If one of the radicals R ¹ , R ² , R ³ , R ⁴ , R ⁵¹ , R ⁵² , R ⁶¹ , R ⁶² , R ⁷¹ and R ^{72 is} an alkenyl radical, this can be straight-chain or branched. It is preferably straight-chain and has 2 to 10 carbon atoms. Accordingly, it means especially vinyl, prop-1- or prop-2-enyl, but-1-, 2- or but-3-enyl, pent-1-, 2-, 3- or pent-4-enyl, hex -1-, 2-, 3-, 4- or hex-5-enyl, hept-1-, 2-, 3-, 4-, 5- or hept-6-enyl, oct-1-, 2-, 3-, 4-, 5-, 6- or oct-7-enyl, non-1-, 2-, 3-, 4-, 5-, 6-, 7- or non-8-enyl, dec-1 -, 2-, 3-, 4-, 5-, 6-, 7-, 8- or dec-9-enyl.

Compounds with branched radicals R ¹ , R ² , R ³ , R ⁴ , R ⁵¹ , R ⁵² , R ⁶¹ , R ⁶² , R ⁷¹ and R ⁷² can occasionally be of importance because of better solubility in the usual liquid-crystalline base materials, but in particular as chiral dopants when they are optically active. Smectic compounds of this type are suitable as components for ferroelectric materials. Connections with SA phases are suitable, for example, for thermally addressed displays.

Branched residues of this type usually contain no more than one Chain branching. Preferred branched wing groups are isopropyl, 2-butyl (= 1-methylpropyl), isobutyl (= 2-methylpropyl), 2-methylbutyl, Isopentyl (= 3-methylbutyl), 2-methylpentyl, 3-methylpentyl, 2-ethylhexyl, 2-propylpentyl, isopropoxy, 2-methylpropoxy, 2-methylbutoxy, 3-methyl butoxy, 2-methylpentoxy, 3-methylpentoxy, 2-ethylhexoxy, 1-methyl hexoxy, 1-methylheptoxy.

The term "alkyl" includes straight and branched chain alkyl groups 1-7 carbon atoms, especially the straight-chain methyl groups, Ethyl, propyl, butyl, pentyl, hexyl and heptyl. Groups of 2-5 coals atoms of matter are generally preferred.

The term "alkenyl" embraces straight-chain and branched alkenyl groups having 2-7 carbon atoms, in particular the straight-chain groups. Particularly alkenyl groups are C ₂ -C ₇ -1E-alkenyl, C ₄ -C ₇ -3E-alkenyl, C ₅ -C ₇ -4-alkenyl, C ₆ -C ₇ -5-alkenyl and C ₇ -6-alkenyl, in particular C ₂ -C ₇ -1 E-alkenyl, C ₄ -C ₇ -3E-alkenyl and C ₅ -C ₇ -4-alkenyl. Examples of preferred alkenyl groups are vinyl, 1E-propenyl, 1E-butenyl, 1E-pentenyl, 1E-hexenyl, 1E-heptenyl, 3-butenyl, 3E-pentenyl, 3E-hexenyl, 3E-heptenyl, 4-pentenyl, 4Z-hexenyl, 4E-hexenyl, 4Z-heptenyl, 5-hexenyl, 6-heptenyl, and the like. Groups of up to 5 carbon atoms are generally preferred.

The compounds of the formulas I to VII and the associated sub-formulas are presented according to methods known per se, as described in the Literature (e.g. in the standard works such as Houben-Weyl, methods of Organic chemistry, Georg-Thieme-Verlag, Stuttgart) are described, under the reaction conditions for those mentioned Implementations are known and suitable. You can also do this from on make use of known variants not mentioned here in greater detail.

The invention also relates to electro-optical displays (in particular other STN or MFK displays with two plane-parallel carrier plates that form a cell with a border, integrated non-linear elements ten for switching individual pixels on the carrier plates and an in nematic liquid crystal mixture with positive dielectric anisotropy and high specific resistance), which the like media as well as the use of these media for electro optical purposes.

The liquid-crystal mixtures according to the invention enable a be significant expansion of the available parameter space.

The achievable combinations of clearing point, viscosity at low temperatures temperature, thermal and UV stability and dielectric anisotropy meet by far previous materials from the state of the art.

The liquid crystal media according to the invention have a clearing point of 100 ° C. or more, preferably 110 ° C. or more, very particularly preferably more than 110 ° C.

The storage stability in TN cells is 500 h or more at -30 ° C, preferably 1000 h or more, and preferably at -40 ° C 200 h or more, in particular 500 hours or more, particularly preferably 1000 hours or more.

The birefringence of the media according to the invention is between 0.07 and 0.10, preferably between 0.075 and 0.095, particularly preferred between 0.08 and 0.09.

The threshold voltage V _{10 of} the liquid crystal media according to the invention in TN cells with dΔn = 0.50 μm is 2.2 V or less, preferably 2.0 V or less, particularly preferably 1.9 V (± 0.1 V) or less.

In particular, the steepness V ₉₀ / V _{10 of} the liquid crystal media according to the invention should be emphasized. In the form V ₉₀ / V ₁₀ -1 53% (± 1% absolute, ie 52 to 54%) or less, preferably 50-48% or less, and particularly preferably 48% or less.

The flow viscosity at -30 ° C. is 1000 mm ² s ^-1 or less, preferably 900 mm ² s ^-1 or less, particularly preferably 750 mm ² s ^-1 or less, and at -40 ° C. 4000 mm ² s ^-1 or less less preferably 3500 mm ² s ^-1 or less and particularly preferably 2800 mm ² s ^-1 or less.

It is understood that by suitable choice of the components of the inven mixtures according to the invention also have higher clearing points (above 110 °) higher threshold voltage or lower clearing points at lower ones Threshold voltages while maintaining the other beneficial property properties can be realized. You can also use accordingly slightly increased viscosities mixtures with larger Δε and thus lower thresholds can be obtained.

The MLC displays according to the invention preferably work in the first Transmission minimum according to Gooch and Tarry [C. H. Gooch and H. A. Tarry, Electron. Lett. 10: 2-4, 1974; C. H. Gooch and H. A. Tarry, Appl. Phys., Vol. 8, 1575-1584, 1975], in addition to particularly favorable electro-optical properties such. B. high steepness of the characteristic and low angle dependence of the contrast (DE-PS 30 22 818) same threshold voltage as in an analog display in the second At least a smaller dielectric anisotropy is sufficient. In this way, using the inventive Mixtures in the first minimum have significantly higher specific resistances realize than with mixtures containing z. B. Connections with Cyano groups. The person skilled in the art can through a suitable choice of the individual Components and their proportions by weight with simple routine method the required for a given layer thickness of the MLC display Adjust birefringence.

The optimal quantitative ratio of the compounds of the formulas I and II + III + IV + V + VI + VII largely depends on the desired Properties, from the choice of components of formulas I, II, III, IV, V, VI and / or VII and from the choice of other, if applicable Components. Suitable proportions within the above specified range can easily be determined from case to case.

The total amount of compounds of the formulas I to VII in the inventions mixtures according to the invention is not critical. The mixtures can therefore contain one or more additional components for the purpose of optimization different properties. The observed effect on the response times and the threshold voltage is usually greater the the total concentration of compounds of the formulas I to VII is higher.

The media according to the invention are preferably based on several Compounds of the formula I, II and III, d. H. the proportion of these compounds is 25 to 95%, preferably 35 to 85% and particularly preferably im Range from 45 to 75%.

Containing media according to the invention are particularly preferred

• - 8 to 40%, in particular 10 to 30%, compounds of the formula I, in particular of the formula Ib,
• - 2 to 20%, in particular 3 to 15%, compounds of the formula II, in particular of the formula IIa,
• - 15 to 70%, in particular 20 to 55%, compounds of the formula III, in particular the formulas IIIa and IIIb,
• - 5 to 35%, in particular 8 to 25%, alkenyl compounds, in particular compounds of the formula Va in which R ⁵¹ and / or R ^{52 are} alkenyl, and compounds of the formula IVa in which R ^{4 is} alkenyl,
• - less than 20%, in particular less than 10%, very particularly preferably no compounds with a 3,4,5-trifluorophenyl group.

The individual compounds of the formulas I to XII and their sub-formulas, which can be used in the media of the invention are either known, or they can be analogous to the known connections genes are produced.

Through a suitable choice of the radicals R ¹ to R ⁷² , the response times, the threshold voltage, the steepness of the transmission characteristics, etc. can be modified as desired. For example, 1E-alkenyl residues, 3E-alkenyl residues, 2E-alkenyloxy residues and the like usually lead to shorter response times, improved nematic tendencies and a higher ratio of the elastic constants K ₃₃ (bend) and K ₁₁ (splay) compared to alkyl or Alkoxy radicals. 4-alkenyl radicals, 3-alkenyl radicals and the like generally give lower threshold voltages and smaller values of K ₃₃ / K ₁₁ compared to alkyl and alkoxy radicals.

A -CH ₂ CH ₂ bridging group generally leads to higher values of K ₃₃ / K ₁₁ compared to a simple covalent bond. Higher values of K ₃₃ / K ₁₁ enable e.g. B. flatter transmission characteristics in TN cells with 90 ° twist (to achieve gray tones) and steeper transmission characteristics in STN, SBE and OMI cells (higher multiplexibility) and vice versa.

The structure of the MLC display according to the invention from polarizers, Electrode base plates and electrodes with surface treatment corresponds to the construction usual for such displays. Here is the The term “usual construction” is broadly defined here and also includes all Variations and modifications of the MLC display, in particular also matrix display elements based on poly-Si TFT or MIM.

A major difference between the displays according to the invention and the hitherto customary based on the twisted nematic cell but in the choice of the liquid crystal parameters of the liquid crystal layer.

The production of the liquid crystals which can be used according to the invention Mixing takes place in the usual manner. Usually the ge desired amount of the components used in a smaller amount in of the components making up the main constituent dissolved, purpose moderate at elevated temperature. It is also possible to use solutions from Com components in an organic solvent, e.g. B. in acetone, chloroform or methanol, to mix and the solvent after mixing to be removed again, for example by distillation.

The dielectrics can also be other ones known to those skilled in the art and described in US Pat Contain additives described in the literature. For example, 0-15% pleochroic dyes or chiral dopants are added.

In the present application and in the examples below, the structures of the liquid-crystal compounds are indicated by acronyms, the transformation into chemical formulas taking place in accordance with Tables A and B below. All of the radicals C _n H _{2n + 1} and C _m H _{2m + 1} are straight-chain alkyl radicals with n and m carbon atoms, respectively. The coding according to Table B is self-evident. In Table A, only the acronym for the basic structure is given. ^{In individual cases, a code for the substituents R 1} , R ² , L ¹ and L ² follows, separated from the acronym for the basic body, with a dash:

Preferred mixture components can be found in Tables A and B.

Table A.

Table B.

The following examples are intended to illustrate the invention without limiting it. Above and below, percentages are percentages by weight. All temperatures are given in degrees Celsius. Also mean
T (N, I) phase transition temperature nematic-isotropic (clearing point),
T (S, N) phase transition temperature smectic-nematic,
t _store storage stability in hours (continuously measured),
ν flow viscosity in mm ² / s (at 20 ° C, unless otherwise stated),
Δn optical anisotropy (589 nm, 20 ° C),
n ₀ ordinary refractive index (589, 20 ° C),
d.Δn optical delay,
d layer thickness,
V ₉₀ / V ₁₀ Slope of the characteristic curve, specified as (V ₉₀ / V ₁₀ - 1) 100%
Threshold voltage = characteristic voltage at a relative contrast of 10%
V ₅₀ characteristic voltage at a relative contrast of 50%,
V ₉₀ characteristic voltage at a relative contrast of 90%,

The electro-optical data were recorded in a TN cell with a 90 ° twist in the 1st minimum (i.e. at a d.Δn value of 0.5 µm) at 20 ° C measured, unless expressly stated otherwise. the optical data were measured at 20 ° C unless explicitly stated something else is stated.

example 1

The following liquid crystal mixture was obtained by the usual method manufactured.

PYP-5F 5.00% CC-5-V 9.00% CCG-V-F 5.00% CCP-20CF3.F 5.00% CCP-30CF3.F 6:00 am% CCP-50CF3.F 6:00 am% CCP-20CF3 5.00% CCP-30CF3 5.00% CCP-40CF3 6:00 am% CCP-50CF3 6:00 am% CDU-2-F 6:00 am% CDU-3-F 6:00 am% CDU-5-F 6:00 am% ECCP-3F.F 6:00 am% ECCP-5F.F 6:00 am% BCH-5F.F 4.00% CCPC-33 4.00% CCPC-35 4.00% T (N, I): 112.5 T (S, N): <-40 t _store (40 ° C): <192 ν (-20 ° C): 256 ν (-30 ° C): 740 ν (-40 ° C): 2670 Δn: 0.0870 n ₀ : 1.4735 V ₁₀ : 1.86 V ₅₀ : 2.23V V ₉₀ : 2.79 V V ₉₀ / V ₁₀ : 50.1%

Example 2

The following liquid-crystal mixture was produced analogously to Example 1 manufactured.

PYP-5F 5.00% CC-5-V 10.00% CCG-V-F 5.00% CCP-20CF3.F 5.00% CCP-30CF3.F 6:00 am% CCP-50CF3.F 6:00 am% CCP-20CF3 5.00% CCP-30CF3 5.00% CCP-40CF3 6:00 am% CCP-50CF3 6:00 am% CDU-2-F 5.00% CDU-3-F 5.00% CDU-5-F 6:00 am% ECCP-3F.F 6:00 am% ECCP-5F.F 6:00 am% BCH-5F.F 5.00% CCPC-33 4.00 CCPC-35 4.00% T (N, I): 112.5 T (S, N): <-40 t _store (-40 ° C): <144 ν (-20 ° C): 256 ν (-30 ° C): 740 ν (-40 ° C): 2670 Δn: 0.0873 n ₀ : 1.4738 V ₁₀ : 1.91 V ₅₀ : 2.28V V ₉₀ : 2.85 V V ₉₀ / V ₁₀ : 49.2%

Claims (10)

1. Liquid-crystal medium based on a mixture of polar compounds with positive dielectric anisotropy, characterized in that it contains one or more compounds of the formula I,
wherein
R ¹ n-alkyl or n-alkoxy with up to 7 carbon atoms, E-alkenyl, alkenyloxy or n-alkoxyalkyl with 2 to 7 carbon atoms, preferably n-alkyl with 2 to 5 carbon atoms,
X ¹ F, OCHF ₂ or OCF ₃ , preferably F and
Y ¹¹ and Y ¹² independently of one another H or F, preferably at least one of the radicals Y ¹¹ and Y ¹² F, particularly preferably both F,
mean,
and contains one or more compounds of the formula II
wherein
R ^{2 has} the meaning given above for R ¹ in formula I and is preferably n-alkyl having 3 to 7, in particular 3 to 5, carbon atoms, and
X ² n-alkyl with 1 to 7 carbon atoms, n-alkoxy with 1 to 5 carbon atoms, F or OCF ₃ , preferably F,
mean. 2. Liquid-crystal medium according to claim 1, characterized in that it additionally contains one or more compounds of the formula III
wherein
R ^{3 has} the meaning given above in formula I for R1 and preferably n-alkyl with 2 to 5 carbon atoms or 1E-alkenyl with 2 to 5 carbon atoms,
X ³ OCHF ₂ or OCF ₃ , preferably OCF ₃ , and
Y ³¹ and Y ³² independently of one another are H or F
mean. 3. Liquid-crystal medium according to claim 1 or 2, characterized in that it additionally contains one or more compounds of the formula IV
wherein
R ^{4 has} the meaning given above in formula III for R ³ , preferably the meaning preferred there,
and
Y ⁴ H or F, preferably H
mean. 4. Liquid-crystal medium according to one of claims 1 to 3, characterized in that it additionally contains one or more compounds of the formula V.
wherein
R ⁵¹ and R ⁵² independently of one another have the meaning given ^{above for R 3 for formula III, R 51} preferably n-alkyl with 2 to 5 carbon atoms and R ⁵² preferably 1E alkenyl with 2 to 5, in particular with 2 or 3 carbon atoms Atoms,
Z ⁵ -COO-, CH ₂ CH ₂ -, -CH = CH- or a single bond
mean. 5. Liquid-crystal medium according to one of claims 1 to 4, characterized in that it additionally contains one or more compounds of the formula VI
wherein
R ⁶¹ and R ⁶² independently of one another have the ^{meaning given above in formula V for R 51} and R ⁵² and preferably n-alkyl having 2 to 5 carbon atoms,
or a single bond and
Z ⁶ -COO- or a single bond, preferably -COO-,
mean. 6. Liquid crystal medium according to one of claims 1 to 5, characterized in that it

• - 8 to 40% of compounds of the formula I, and
• - 2 to 20% compounds of the formula II,

contains. 7. Liquid crystal medium according to one of claims 1 to 6, characterized in that it

• - 15 to 70% of compounds of the formulas IIIa and IIIb, and
• - 5 to 35% of compounds of the formula Va in which R ⁵¹ and / or R ^{52 are} alkenyl, and compounds of the formula IVa in which R4 is alkenyl,

contains. 8. Liquid crystal medium according to one of claims 1 to 7, characterized characterized in that there are less than 70% compounds with one Contains 3,4,5-trifluorophenyl group 9. Use of a liquid crystal medium according to one of the claims 1 to 8 for electro-optical purposes. 10. Electro-optical liquid crystal display containing a Liquid crystal medium according to one of Claims 1 to 8.